aromatic compounds: ring activators and directors

[wooki]

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how often has this shown up on the MCAT? do you guys memorize specific substituents that are good activators and deactivators? ones that direct para, meta, ortho, etc?

any insight is appreciated. thx!

 

[Kaustikos]

how often has this shown up on the MCAT? do you guys memorize specific substituents that are good activators and deactivators? ones that direct para, meta, ortho, etc?

any insight is appreciated. thx!

It's not that it doesn't show up often, but that you should still be familiar with it.

Knowing which types of compounds tend to be deactivating (meta) vs activating (ortho, para) doesn't necessarily take long to get down and helps eliminate questions. From tests I have taken, they've been there, but not in a large amount. More or less discretes and occasionally passages.

Lastly, knowing the background of the substituents is definitely a plus for the mcat. Knowing WHY compounds are activating (donating) vs deactivating (withdrawing) is EXTREMELY beneficial because it answers aromatics and various other questions that might arise from knowing this
ie: the acidity/basicity of multisubstituted vs mono-substituted alkanes.

 

[secants]

Just curious, but wasn't benzene not being tested anymore in Organic-Chem for MCATS?

 

[wooki]

deactivating (meta) vs activating (ortho, para) doesn't necessarily take long to get down and helps eliminate questions.

i didnt realize metas didnt have activating groups. but i was trying to figure out if i should memorize things like

meta ring deactivators: NR3, NO2, SO3H...

ortho/para ring activator: NR2, OH..

thanks for ur replies!

 

[BerkReviewTeach]

Just curious, but wasn't benzene not being tested anymore in Organic-Chem for MCATS?

Electrophilic aromatic substitution of benzene compounds was dropped from their list in 2003. But, the concept of activation and deactivation (through resonance and the inductive effect) is fair game when considering the acidity of phenols and benzoic acid.

And to address the other question here, it would seem that it is hard to say what is fair game given that they test so little organic chemistry on the test these days. I assume there are many topics that are fair territory that just don't get tested because they have so little o chem on the exam.

The general feeling in the MCAT threads seems to be that if you know your basic concepts really well and have some understanding of a few common reactions and lab techniques, then you'll be fine in organic.